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The present invention relates to electronic throttle controllers for vehicles and in particular to such controllers providing automated speed control.
Electronic throttle controllers are well known for operating an engine throttle valve to control the rate of fuel flow to the combustion chamber of an engine. Typically, the throttle controller receives an acceleration input signal from the operator of the vehicle via an accelerator pedal. The farther the pedal is depressed, the more the throttle valve is opened, which permits more fuel to be consumed by the engine and the vehicle to travel faster.
Some throttle controllers can operate automatically as a xe2x80x9ccruise controlxe2x80x9d to maintain the speed of the vehicle at a cruising speed set by the driver. The cruise control provides a convenient means for a driver to maintain vehicle speed without using foot pedals, which can be especially advantageous on long trips. Typically, such cruise controls use an input from a speedometer or engine speed sensor to monitor the cruising speed of the vehicle. Due to varying terrain, friction and wind resistance the speed controller is nearly continuously correcting for deviations from the desired speed. Consequently, the throttle is constantly fluctuating to allow more or less fuel to be consumed by the engine to maintain the set speed.
A problem with such cruise controls is that the continuous throttle adjustments lower the fuel economy of the engine. This is primarily due to the inefficiencies involved with non-constant burning, which include counteracting momentum losses of the moving components of the engine as well as that of the overall vehicle.
Most cruise controls include stored error correction algorithms that define the response time and duration of the throttle adjustments. These algorithms are commonly designed with smoothness, accuracy and responsiveness being the highest priorities. Fuel economy is typically not a factor in the design of the algorithms.
Yet, U.S. Pat. No. 5,944,766 discloses a cruise control having control algorithms designed to improve the fuel economy of the vehicle. When it is sensed that the vehicle is gaining momentum, the algorithms instruct the speed controller to override the normal control of the throttle and set back the throttle position to a prescribed percentage (such as 50% or 80%) of its normal position. Thus, fuel consumption is minimized during and after the vehicle travels down hill. As such, the disclosed cruise control has only limited fuel saving benefits.
Accordingly, there exists a need for a cruise control with improved fuel economizing benefits.
The present invention provides a vehicle cruise control with a fuel economy cruise mode that reduces the amount of fuel consumed by the vehicle. In the fuel economy cruise mode, the cruise control eliminates changes in engine throttling within a given deviation from the desired cruising speed. Moreover, the cruise control can provide initial throttle adjustment at less than normal rates during and when exiting the fuel economy cruise mode. Thus, the present invention reduces fuel costs and exhaust emissions into the environment
Specifically, the present invention provides a cruise control designed for use with engines having an electronically controlled throttle valve movable to regulate fuel flow to the engine. The cruise control has an electronic control module electrically coupled to the throttle for controlling the position of the throttle valve and an input device operable from within a passenger cabin of the vehicle for signaling the control module of a speed signal corresponding to a desired vehicle speed to be maintained. The control module enters a fuel economy cruise mode and fixes the position of the throttle valve when the speed set signal is received and the vehicle speed is within a prescribed error range from the desired vehicle speed for a prescribed time period. The control module maintains the fixed position of the throttle valve until an exit condition or an acceleration/deceleration input is detected.
In a preferred form, the control module includes an input module, a memory module and a processor electrically coupled together. The prescribed error range and time period are stored in memory. Preferably, the prescribed error range two miles per hour and the prescribed time period is 10-30 seconds. Upon detecting an exit condition (or acceleration input), the control module can provide initial or sustained speed adjustment set backs, or in other words, less than normal acceleration and deceleration.
In one preferred form, the cruise control can also operate in a conventional cruise mode, activated by the input device, in which the control module repositions the throttle valve at prescribed intervals to maintain the desired vehicle speed according to speed adjustment gains of cruise control algorithms. When an exit condition is detected, the speed control module repositions the throttle valve so as to limit the rate of change of vehicle speed to less than the rate of change of speed ordinarily allowed during cruise mode. Additionally, the input device can send acceleration/deceleration signals to the control module, in which case, the control module repositions the throttle valve according to algorithms having reduced speed adjustment gains from that of the cruise mode algorithms. Preferably, the reduced speed algorithms are stored in the memory module.
The cruise control can also include an engine speed sensor coupled to the control module for sending the control module current vehicle speed data. The control module can be electrically coupled to a transmission clutch, a brake and a battery of the vehicle. For such a vehicle, the exit conditions can include, among others, an off input signal, a low speed input, a brake input signal, a clutch activation signal, a low battery signal and combinations thereof.
The present invention also provides a method of reducing the fuel consumption of an vehicle having a cruise control with a control module operated by an input device mounted within a passenger cabin of the vehicle. The method includes receiving operator inputs for a desired vehicle speed and to a begin fuel economy cruise mode; verifying that the vehicle is traveling within a prescribed range of the desired vehicle speed for a prescribed time period; entering a fuel economy cruise mode and fixing the position of the throttle; checking for an exit condition and acceleration/deceleration input; and maintaining the throttle at the fixed position until either the exit condition or acceleration/deceleration input is detected.
The method can further include the step of reducing vehicle acceleration and deceleration input from the operator when exiting fuel economy cruise mode. Preferably, this is done by the control module processor processing speed adjustment algorithms stored in the memory module to reduce the vehicle acceleration/deceleration rate during and when exiting the fuel economy cruise mode.
Thus, the present invention provides a cruise control using less fuel than conventional cruise controls, thereby reducing fuel costs and exhaust emissions into the environment. During fuel economy cruise mode all engine throttling is eliminated when the vehicle is traveling withing a range of the desired speed. Moreover, the cruise control applies reduced acceleration gains when accelerating or decelerating while in the fuel economy cruise mode or when returning to the conventional manual or cruise modes.